Repairing a distressed and cracked road surface by applying an overlay to the road surface is well known. This method for repairing cracked roads, however, has many drawbacks, including reflective cracking, which may occur in the overlay.
When an overlay is applied over a crack or a joint in the road to be repaired, physical tearing of the overlay may take place due to various stresses to which the overlay is subjected. As a result, the crack or joint in the pavement can reflect up into the overlay and the overlay also becomes cracked above the crack or joint in the pavement. FIG. 1 shows a reflected crack in an overlay.
Reflection cracking has occurred in nearly all types of overlays, but is more common in asphalt concrete overlays placed on rigid pavements. When an asphalt concrete overlay is placed upon a rigid pavement, any movement that occurs in the underlying pavement at a crack or joint will produce stress in the overlay and can cause physical tearing of the overlay if the stress in the overlay exceeds the tensile strength of the overlay.
Movement in the underlying pavement can be caused by several factors, including seasonal temperature changes, daily temperature changes and traffic loads. For example, the low temperatures encountered during winter causes the pavement under an overlay to contract. Typically, when the pavement contracts, the cracks in the pavement widen and the stress in the overlay, which is bonded to the pavement, is proportional to the movement taking place at the site of the crack. However, the overlay also contracts in response to low temperatures. The contraction of the overlay directly above the crack provides further stress in the overlay.
In addition to seasonal temperature changes, daily temperature changes also create stress in the overlay. While the stresses in the overlay that are induced by daily temperature changes are not as great as the stresses induced by seasonal temperature changes because the temperature variations are not as extreme, daily temperature changes are more frequent.
Another source of stress in the overlay is the traffic load, which can hasten reflective cracking.
The present invention provides a stress absorbing composite that is placed over cracked pavement before an overlay is applied to the pavement. The stress absorbing composite is able to absorb and dissipate some of the stress to which the overlay would normally be subjected. Because the stress absorbing composite helps to reduce the stress in the overlay, repaired roads that use a stress absorbing composite of the present invention last longer and reflective cracking of the overlay is retarded.